The device herein is used in connection with an air filter for an internal combustion engine. Said device indicates by a visible linear indication the accumulation of contaminants present in the filter placing restriction upon the air stream passing through the filter and said device further shows when the air filter has become loaded with such an accumulation of contaminants that an air stream or the combustion air can no longer in sufficient quantity pass through the filter to supply the requirement for air for efficient operation of the engine.
The device herein gives a continuous reading to indicate the build up of contaminants within an air filter to inform visibly how much usefulness is left in the air filter. The device herein does away with guess work as to the time when cleaning or replacement of the air filter is necessary and provides for maximum use of an air filter.
The device herein provides specific improvements over the structure of the copending application Ser. No. 521,697 filed Nov. 7, 1974 by the inventor herein, said improvements consisting in having the indicating member and directly related parts in a chamber sealed against outside air being drawn therein which air would bring in contaminants and the diaphragm is arranged to have a greater effective surface area engaged by atmospheric pressure to make the device capable of providing a more sensitive indication of restriction, as will be described.
It is an object of this invention to provide a device which gives a positive indication by a visible reading of the need for cleaning or replacing an air filter.
It is another object of this invention in connection with an air filter for an internal combustion engine to give a continuous visual reading of the condition of an air filter by a visible reading of a linear indicator.
More particularly stated, it is an object of this invention to provide a device as above indicated which is of a simple construction and which is readily installed in operating position such as to be readily visible to an operator.
It is also an object of this invention to provide a device to detect the restriction being placed upon an air stream passing through an air filter which device comprises a housing having a linear moveable indicating member therein bearing a readily seen color to indicate the relative condition of an air filter as to the build up of contaminants therein and as to the restriction being placed on an air stream passing therethrough and also having a readily seen indicating member which indicates that the air filter for practical purposes may be regarded as being fully restricted with respect to the further passage of air therethrough in sufficient quantity to support combustion in an internal combustion engine, said device having a diaphragm therein adjusted for a normal operating condition as with the filter free from contamination, to provide a balance between the atmospheric pressure upon one side thereof and the partial vacuum drawn upon the other side thereof which results from the normal operation of the engine.